18... h8h5 Ding is careless with the c2-bishop. He certainly miscalculated something. 19. e2e4 Now the bishop is trapped and will eventually be captured. Black won't have enough compensation for the piece. Although there's still a lot of play left, there is a major shift in the assessment of the position. Furthermore, Gukesh had a large advantage on the clock at this point. 19... d5e4 A mistake never comes alone. That is one of the universal chess truths. 20. f3e4  20... g7e6 